Less frequent causes of lower gastrointestinal bleeding.

In the United States, four diseases account for the vast majority of cases of lower intestinal bleeding: arteriovenous malformation, diverticulosis, neoplasms, and internal hemorrhoids. In this article the authors discuss less frequent causes of gastrointestinal bleeding. "Common" less frequent causes of gastrointestinal bleeding include solitary rectal ulcer syndrome, colonic varices, mesenteric vascular insufficiency, small bowel diverticula, Meckel's diverticulum, aortoenteric fistula, vasculitis, small intestinal ulceration, endometriosis, radiation-induced injury, and intussusception. Less frequent causes of gastrointestinal bleeding that have been recently described include portal colopathy, diversion colitis, and gastrointestinal bleeding in runners.